In thermally assisted optical/magnetic data storage, information bits are recorded on a layer of a storage medium at elevated temperatures, and the heated area in the storage medium determines the data bit dimension. Heat assisted magnetic recording (HAMR) generally refers to the concept of locally heating a recording medium to reduce the coercivity of the recording medium so that the applied magnetic writing field can more easily direct the magnetization of the recording medium during the temporary magnetic softening of the recording medium caused by the heat source. For heat assisted magnetic recording (HAMR) a tightly confined, high power laser light spot is used to preheat a portion of the recording medium to substantially reduce the coercivity of the heated portion. Then the heated portion is subjected to a magnetic field that sets the direction of magnetization of the heated portion. In this manner the coercivity of the medium at ambient temperature can be much higher than the coercivity during recording, thereby enabling stability of the recorded bits at much higher storage densities and with much smaller bit cells. Heat assisted magnetic recording can be applied to any type of magnetic storage media, including tilted media, longitudinal media, perpendicular media and patterned media.
In HAMR disc drives, it is desirable to efficiently deliver the laser light to the recording head. One approach would be to place a laser source directly on the slider. However, that approach requires additional electrical connections to the slider for the laser. Also, the electrical power dissipated by the laser will substantially heat the slider, which is undesirable for obtaining the best performance from the reader. The added mass of the laser on the slider (or suspension assembly) may also degrade the dynamic and shock performance of the suspension.
Alternatively, a laser source can be located elsewhere in the disc drive and its emitted light carried to the slider through an optical fiber. This approach eliminates the problems with the laser on the slider mentioned above, but introduces a new problem, which is how the optical connection is made between the fiber and the slider. Optical fiber is typically very stiff. If the fiber is physically attached to the slider, the stiffness complicates the design of the gimbal structure that allows the slider to fly over the surface of the disc. Therefore, it is desirable to have a small free space gap between the end of the fiber and the slider. The fiber should be brought to the slider along the suspension and then positioned so that the emitted light illuminates the optical transducer on the slider. One way that has been proposed to do this is to include a mirror or prism on the suspension to direct the laser beam toward the slider.
One of the requirements for a heat assisted magnetic recording drive is an effective way to couple light from a laser diode or fiber to the coupling grating on the slider. A number of methods have been suggested to date which either require either direct bonding of a fiber to the slider, a significant modification to the slider (such as a deep trench for optics), or the slider flying 180 degrees rotated from its current position. These methods require a major redesign of the air bearings, suspensions and load beams.
A number of different light delivery options for Heat Assisted Magnetic Recording (HAMR) have been proposed. One of the leading ideas is the fiber lens focusing onto a grating on a reversed slider. That method provides a simple optical path and allows for compensation of the vertical motion of the slider during operation due to disk vertical run out. It has the disadvantage of the cost of a fiber pigtailed laser and because of its location it will be difficult to align the fiber lens during manufacturing.
Also, polarization maintaining or polarizing fibers may be required to produce stable and efficient delivery of transverse electric (TE) light to the gratings. These fiber types greatly increase the cost of the pigtailed laser diode and the alignment difficulty due to the rotational requirements.
There is a need for a recording device that can provide localized heating of a recording medium without the need for optical fiber or multiple optical components.